正常照明断电时投入运行的应急照明，不能选用( )作为光源。

A．白炽灯

B．卤钨灯

C．冷阴极荧光灯

D．金卤灯

The key ( ) the company's success was that it employed an excellent manager.

A. to
B. for
C. around
D. about